Abstract
The purpose of the present study was to investigate the changes of the electromyographic (EMG) activities of the perioral muscles during sucking periods in infants.
Forty infants (23 males,17 females, mean age: 14.2 wks after birth) were the subjects of the evaluation. EMGs were able to be obtained from 4 perioral muscles such as the unilateral temporalis (TM), masseter (MM), orbicularis oris (OM) and suprahyoid muscles (SM) from the start to the end of feeding. Comparisons were also made between breast feeding (BRF,20 infants) and bottle feeding (BOF,20infants). The evaluation parameters employed were the EMG activities (μV, peak to peak), the frequency of sucking burst (%) presented in the EMG and the ratio of each muscle activity (%) to the total muscle activity found in the first consecutive sucking EMG bursts. Those bursts were further subdivided into three periods according to the sucking time such as the early, middle and late periods.
The following results were obtained:
1) Each muscle activity varied according to the subject, muscles and sucking period. The muscle activities of the four muscles decreased with the sucking time. The SM was the most active, followed by the OM, MM and TM. Total muscle activity also showed differences among the subjects and the sucking period.
2) The BRF showed higher EMG activity than BOF in the MM, OM, SM and the total muscle activity.
3) The ratio of each muscle activity to the total activity was 9.5% in the TM,12.0% in the MM,28.0% in the OM,50.5% in the SM in the BRF infants, and 11.0%,11.5%,27.5% and 49.0% in the BOF infants, respectively. There were no differences in the ratio in each muscle between the BRF and BOF group, and in the sucking periods.
4) The frequencies of the EMG bursts for sucking showed the highest in the OM and SM, and followed by the MM and TM, and it declined with the passing of time in the MM and TM, but not changed in the OM and SM. It may be concluded that the SM and OM function mainly during sucking movement both in breast and bottle feeding infants, and the muscle activities of each muscle decrease with sucking time, while the ratio of each muscle activity to total muscle activity does not vary.
